Brand of lye makes a difference?

[Carly B]

I've been soaping for about a year and a half--I'm still in that stage where it's fun playing with SoapCalc and experimenting
with different oils. Other than my brine soap, which friends and family have specifically requested, I don't think I've done the
exact same recipe twice. The only constant has been the lye.

But the last few batches of soap I've made, I've noticed that after 24 hours, they're still really soft, even the batches that have a high
percentage of harder oils. When they do come out of the mold, they're sticky, and really soft inside. And the stickiness seems to last
about a week or so, although they do eventually harden up. I thought maybe it was because I add silk to the masterbatched lye, but no, I've
had batches of soap with silk that have been quite hard within hours.

So I puzzled over it, and realized that the last masterbatch of lye I made was with a different brand of lye. I've always used Comstar lye in
the past, but this last masterbatch was made with Belle Chemical lye. I even made a batch of the brine soap, and it didn't harden up right
away like the other batches of brine soap I made.

Am I just grasping at straws looking for an answer? When I get more Comstar lye I'm going to replicate the batch I just made to compare, but in the interim,
has anyone else noticed different results depending upon the brand of lye?

 

[Babyshoes]

In theory, it shouldn't if both are 100% pure. Have you checked the container to ensure its not adulterated?

I guess it could also be an issue if the container wasn't properly sealed and got a bit of moisture in it?

 

[jcandleattic]

Sounds like you got a bad batch of lye because it shouldn't make a difference if both are 100% sodium hydroxide.
(no lye is 100% pure, but all should be within a range that you would not see a noticeable difference like that)

 

[DeeAnna]

No chemical, including NaOH, will ever be 100% pure. Commercial NaOH is typically 92% to 97% pure coming direct from the manufacturer. If the NaOH is stored in a way that excludes moisture and air, the NaOH should stay at that or near that purity indefinitely. Your supplier should be able to tell you what the as-received purity is. You need to be storing the NaOH properly, because how you handle it will also make a big difference in the long-term purity.

There are only a few producers of NaOH in the US (Dow and Occidental are two that I can think of), but there are many suppliers who buy their NaOH and repackage it for their customers. It's hard to know in your case whether your problems are related to the NaOH or related to something else. But if you suspect it's a purity issue, compare what you used to buy with what you're using now and see if there's a trend.

 

[AliOop]

Since you are master-batching, it might be wise to decant what you have left into another container, and check for any lye crystalization on the bottom of the container. That can happen if the lye wasn't completely dissolved at the start, or if the solution was subjected to temps below 65F or so. The result is that the lye solution which you believe is 50-50 may be quite a bit less than that.

Also, after double-checking that the cap is on tightly, I always lightly shake my MB jug to remix everything before measuring it out.